[222] | 1 | // -*- C++ -*- |
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| 2 | /* |
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| 3 | *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> > |
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| 4 | * |
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| 5 | *Constructor: |
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| 6 | * |
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| 7 | *Dijkstra(Graph G, LengthMap length) |
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| 8 | * |
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| 9 | * |
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| 10 | *Methods: |
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| 11 | * |
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| 12 | *void run(Node s) |
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| 13 | * |
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| 14 | *T dist(Node v) : After run(s) was run, it returns the distance from s to v. |
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| 15 | * Returns T() if v is not reachable from s. |
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| 16 | * |
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| 17 | *Edge pred(Node v) : After run(s) was run, it returns the last |
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| 18 | * edge of a shortest s-v path. It is INVALID for s and for |
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| 19 | * the nodes not reachable from s. |
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| 20 | * |
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| 21 | *bool reached(Node v) : After run(s) was run, it is true iff v is |
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| 22 | * reachable from s |
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| 23 | * |
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| 24 | */ |
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| 25 | |
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| 26 | #ifndef HUGO_DIJKSTRA_H |
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| 27 | #define HUGO_DIJKSTRA_H |
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| 28 | |
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| 29 | #include <fib_heap.h> |
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[228] | 30 | #include <bin_heap.hh> |
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[222] | 31 | #include <invalid.h> |
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| 32 | |
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| 33 | namespace hugo { |
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| 34 | |
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| 35 | //Alpar: Changed the order of the parameters |
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[224] | 36 | |
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| 37 | ///Dijkstra algorithm class. |
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| 38 | |
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| 39 | ///This class provides an efficient implementation of Dijkstra algorithm. |
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| 40 | ///The edge lengths are passed to the algorithm using a |
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| 41 | ///\ref ReadMapSkeleton "readable map", |
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| 42 | ///so it is easy to change it to any kind of length. |
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| 43 | /// |
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| 44 | ///The type of the length is determined by the \c ValueType of the length map. |
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| 45 | /// |
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| 46 | ///It is also posible to change the underlying priority heap. |
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| 47 | /// |
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| 48 | ///\param Graph The graph type the algorithm runs on. |
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| 49 | ///\param LengthMap This read-only EdgeMap determines the |
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| 50 | ///lengths of the edges. It is read once for each edge, so the map |
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| 51 | ///may involve in relatively time consuming process to compute the edge |
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| 52 | ///length if it is necessary. |
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| 53 | ///\param Heap The heap type used by the Dijkstra |
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| 54 | ///algorithm. The default |
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| 55 | ///is using \ref BinHeap "binary heap". |
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[222] | 56 | template <typename Graph, |
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| 57 | typename LengthMap=typename Graph::EdgeMap<int>, |
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[228] | 58 | typename Heap=BinHeap <typename Graph::Node, |
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| 59 | typename LengthMap::ValueType, |
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| 60 | typename Graph::NodeMap<int> > > |
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[222] | 61 | class Dijkstra{ |
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| 62 | public: |
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[228] | 63 | typedef typename Graph::Node Node; |
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| 64 | typedef typename Graph::NodeIt NodeIt; |
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| 65 | typedef typename Graph::Edge Edge; |
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| 66 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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| 67 | |
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[222] | 68 | typedef typename LengthMap::ValueType ValueType; |
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[224] | 69 | typedef typename Graph::NodeMap<Edge> PredMap; |
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| 70 | typedef typename Graph::NodeMap<Node> PredNodeMap; |
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| 71 | typedef typename Graph::NodeMap<ValueType> DistMap; |
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[222] | 72 | |
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| 73 | private: |
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| 74 | const Graph& G; |
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| 75 | const LengthMap& length; |
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| 76 | PredMap predecessor; |
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| 77 | //In place of reach: |
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| 78 | PredNodeMap pred_node; |
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| 79 | DistMap distance; |
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| 80 | //I don't like this: |
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| 81 | // //FIXME: |
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| 82 | // typename Graph::NodeMap<bool> reach; |
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| 83 | // //typename Graph::NodeMap<int> reach; |
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| 84 | |
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| 85 | public : |
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| 86 | |
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| 87 | /* |
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| 88 | The distance of the nodes is 0. |
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| 89 | */ |
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| 90 | Dijkstra(Graph& _G, LengthMap& _length) : |
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| 91 | G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { } |
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| 92 | |
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| 93 | |
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| 94 | void run(Node s); |
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| 95 | |
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[224] | 96 | ///The distance of a node from the source. |
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| 97 | |
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| 98 | ///Returns the distance of a node from the source. |
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| 99 | ///\pre \ref run() must be called before using this function. |
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| 100 | ///\warning If node \c v in unreachable from \c s the return value |
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| 101 | ///of this funcion is undefined. |
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[222] | 102 | ValueType dist(Node v) const { return distance[v]; } |
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[224] | 103 | ///Returns the edges of the shortest path tree. |
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| 104 | |
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| 105 | ///For a node \c v it returns the last edge of the shortest path |
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| 106 | ///from \c s to \c v or INVALID if \c v is unreachable from \c s. |
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| 107 | ///\pre \ref run() must be called before using this function. |
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[222] | 108 | Edge pred(Node v) const { return predecessor[v]; } |
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[224] | 109 | ///Returns the nodes of the shortest paths. |
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| 110 | |
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| 111 | ///For a node \c v it returns the last but one node of the shortest path |
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| 112 | ///from \c s to \c v or INVALID if \c v is unreachable from \c s. |
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| 113 | ///\pre \ref run() must be called before using this function. |
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[222] | 114 | Node predNode(Node v) const { return pred_node[v]; } |
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| 115 | |
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[224] | 116 | ///Returns a reference to the NodeMap of distances. |
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| 117 | |
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| 118 | ///\pre \ref run() must be called before using this function. |
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| 119 | /// |
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[222] | 120 | const DistMap &distMap() const { return distance;} |
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[224] | 121 | ///Returns a reference to the shortest path tree map. |
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| 122 | |
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| 123 | ///Returns a reference to the NodeMap of the edges of the |
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| 124 | ///shortest path tree. |
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| 125 | ///\pre \ref run() must be called before using this function. |
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[222] | 126 | const PredMap &predMap() const { return predecessor;} |
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[224] | 127 | ///Returns a reference to the map of nodes of shortest paths. |
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| 128 | |
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| 129 | ///Returns a reference to the NodeMap of the last but one nodes of the |
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| 130 | ///shortest paths. |
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| 131 | ///\pre \ref run() must be called before using this function. |
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[222] | 132 | const PredNodeMap &predNodeMap() const { return pred_node;} |
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| 133 | |
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| 134 | // bool reached(Node v) { return reach[v]; } |
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[224] | 135 | |
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| 136 | ///Chech if a node is reachable from \c s. |
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| 137 | |
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| 138 | ///Returns \c true if \c v is reachable from \c s. |
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| 139 | ///\warning \c s is reported to be unreached! |
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| 140 | ///\todo Is this what we want? |
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| 141 | ///\pre \ref run() must be called before using this function. |
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[222] | 142 | /// |
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| 143 | bool reached(Node v) { return G.valid(predecessor[v]); } |
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| 144 | |
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| 145 | }; |
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| 146 | |
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| 147 | |
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[224] | 148 | // ********************************************************************** |
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| 149 | // IMPLEMENTATIONS |
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| 150 | // ********************************************************************** |
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[222] | 151 | |
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[224] | 152 | ///Runs Dijkstra algorithm from node \c s. |
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| 153 | |
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| 154 | ///This method runs the Dijkstra algorithm from node \c s in order to |
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| 155 | ///compute the |
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| 156 | ///shortest path to each node. The algorithm computes |
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| 157 | ///- The shortest path tree. |
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| 158 | ///- The distance of each node. |
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[222] | 159 | template <typename Graph, typename LengthMap, typename Heap > |
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| 160 | void Dijkstra<Graph,LengthMap,Heap>::run(Node s) { |
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| 161 | |
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| 162 | NodeIt u; |
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| 163 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) { |
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| 164 | predecessor.set(u,INVALID); |
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[224] | 165 | pred_node.set(u,INVALID); |
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[222] | 166 | // If a node is unreacheable, then why should be the dist=0? |
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| 167 | // distance.set(u,0); |
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| 168 | // reach.set(u,false); |
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| 169 | } |
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| 170 | |
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| 171 | //We don't need it at all. |
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| 172 | // //FIXME: |
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| 173 | // typename Graph::NodeMap<bool> scanned(G,false); |
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| 174 | // //typename Graph::NodeMap<int> scanned(G,false); |
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| 175 | typename Graph::NodeMap<int> heap_map(G,-1); |
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| 176 | |
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| 177 | Heap heap(heap_map); |
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| 178 | |
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| 179 | heap.push(s,0); |
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| 180 | // reach.set(s, true); |
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| 181 | |
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| 182 | while ( !heap.empty() ) { |
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| 183 | |
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| 184 | Node v=heap.top(); |
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| 185 | ValueType oldvalue=heap[v]; |
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| 186 | heap.pop(); |
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| 187 | distance.set(v, oldvalue); |
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| 188 | |
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| 189 | for(OutEdgeIt e(G,v); G.valid(e); G.next(e)) { |
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| 190 | Node w=G.head(e); |
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| 191 | |
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| 192 | switch(heap.state(w)) { |
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| 193 | case Heap::PRE_HEAP: |
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| 194 | // reach.set(w,true); |
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| 195 | heap.push(w,oldvalue+length[e]); |
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| 196 | predecessor.set(w,e); |
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| 197 | pred_node.set(w,v); |
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| 198 | break; |
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| 199 | case Heap::IN_HEAP: |
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| 200 | if ( oldvalue+length[e] < heap[w] ) { |
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| 201 | heap.decrease(w, oldvalue+length[e]); |
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| 202 | predecessor.set(w,e); |
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| 203 | pred_node.set(w,v); |
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| 204 | } |
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| 205 | break; |
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| 206 | case Heap::POST_HEAP: |
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| 207 | break; |
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| 208 | } |
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| 209 | } |
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| 210 | } |
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| 211 | } |
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| 212 | |
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| 213 | } //END OF NAMESPACE HUGO |
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| 214 | |
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| 215 | #endif |
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| 216 | |
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| 217 | |
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